FTIR-emission measurements of the polar Arctic atmosphere were made in Ny-Ålesund (79°N, 11°E) with commercially available instruments. The infrared emission spectra were analysed with the FASCOD3 algorithm and home .made analysis software. In order to get an agreement between experiment and simulation and to retrieve the correct column amounts of trace gases present in the atmosphere, the contribution of aerosols had to be included in subsequent radiative transfer calculations. We varied the aerosol optical depth by the parameter of the visibility in FASCOD3 in selected spectral microwindows, which are not superimposed by molecular emission bands. Furthermore, the optical depth was measured with a sun (under daylight conditions) or a star photometer (during polar night) in the UV/Visible-range. The comparison of the UV/Visible-data with the results from the FTIR-emission measurements shows a strong decay in the optical depth of the tropospheric aerosols over the two spectral regions. Copyright 1999 by the American Geophysical Union.